Document processing devices include printers, copiers, scanners and e-mail gateways. More recently, devices employing two or more of these functions are found in office environments. These devices are referred to as multifunction peripherals (MFPs) or multifunction devices (MFDs). As used herein, MFP means any of the forgoing.
An electrostatic process unit (EPU) in many toner-based printers and multifunction peripherals performs the printing function. The EPU typically comprises a photoconductive drum, and a developer roller, and can include a charge unit, a toner hopper, a semiconductor laser, and developer among other components as would be known in the art. The EPU can be configured as a field replaceable unit or can be part of a self-contained compact cartridge that includes the toner. Using magnetic and electrostatic forces, the developer roller and the photoconductive drum transfer toner from a toner hopper to a sheet of paper where it is fused by heat to the paper. After the photoconductive drum transfers toner to the paper, a cleaner blade in the EPU removes residual toner and paper dust from the photoconductive drum.
During normal operation residual toner and paper dust can leak through seals into unintended areas of the EPU causing operational problems. For example, small amounts of stray toner can move along rotating shafts of components inside the EPU and leak through sealing areas intended to prevent that toner from entering bearings or leaking to other parts of the printer. Toner leakage can interfere with the proper operation of the electrostatic process unit as well as other parts of the printer.